1. Technical Field
This invention is related to the field of ignition diagnosis systems of automotive internal combustion engines. More particularly, it is related to the field of ignition diagnosis and control systems, and the ability to pre-condition the ionization signal such that the knock component of the ionization signal can be more easily processed and analyzed.
2. Discussion
The prior art includes a variety of conventional methods for detecting and using ionization current in a combustion chamber of an internal combustion engine. One of the more commonly known uses of the ionization signal is to detect, and therefore control the ignition system to prevent, engine knock.
It is well known in the art to determine the presence and intensity of knock from the in-cylinder ionization signal, e.g., as described in U.S. Pat. No. 6,945,229 (“the '229 Patent”), the entire disclosure of which being hereby incorporated by reference. Typically, and as described in the '229 Patent, ionization detection circuitry provides a single ionization output signal that is sent from a cylinder to the powertrain control module (PCM). The PCM processes the ionization signal, e.g., by conditioning, bandpass filtering and amplifying the signal, and derives knock information therefrom. It is common for an Application Specific Integrated Circuit (“ASIC”) to calculate this knock information, although other systems and methods may be used (for example, a microprocessor with appropriate software may be substituted for the ASIC).
The typical method of detecting engine knock from the ionization signal is to separate the knock frequencies of the ionization signal, amplify those frequencies and present the amplified, knock-enhanced ionization signal to an ASIC or a microcontroller analog-to-digital converter. There are a number of limitations with this current design, including the additional cost of adding circuitry/functionality to the PCM to process the ionization signal before presenting it to the ASIC or microcontroller analog-to-digital converter, as well as the additional channels needed to accept the input of the amplified, knock-enhanced ionization signal separate from and in addition to the ionization signal. A system and method that allows for the pre-conditioning and amplifying of the knock portion of the ionization signal within the ionization detection circuitry such that the PCM can be spared this extra complexity and expense.